The selectins are highly selective C-type lectins that bind sialyI-Lewis x (sLex)-related glycans. A sLex-modified core 2 O-glycan (C2-O-sLex) expressed on the surface of leukocytes has been directly demonstrated to confer significantly higher affinity selectin binding than sLex in leukocyte adhesion events. Increasing evidence indicates the importance of selectin-dependent cell binding in the extravasation of blood-circulating tumor cells. As with leukocytes, C2-O-sLex may promote high affinity binding of carcinoma cells to the selectins and enhance adhesion to endothelium and subsequent metastasis. However, the ability of C2-O-sLex to act as a selectin ligand has not been directly examined. We have recently described a novel monoclonal antibody, CHO-131, that selectively recognizes C2-O-sLex and determined its reactivity with colon carcinoma cells. Thus, the central hypothesis for the proposed research is that C2-O-sLex on colon carcinoma cells is a high affinity ligand for selectin binding and increases the metastatic ability of tumor cells. Aim 1 will determine the selectin binding characteristics of colon carcinoma cells expressing C2-O-sLex and sLex under hydrodynamic shear stress conditions that simulate blood flow in the microvasculature. In Aim 2, we will compare the ability of C2-O-sLex- and sLex-expressing colon carcinoma cells to metastasize to the liver, lung, and bone marrow using an in vivo murine model. Aim 3 will investigate the expression of C2-O-sLex on colon carcinoma cells in benign and malignant human colonic tissues by immunohistochemistry. Significant positive impacts of our studies include the development of novel strategies directed at preventing colon carcinoma invasion and metastasis, the development of new prognostic markers of disease, and a considerable increase in the long-term survival of patients with colorectal cancer. This K08 award will strengthen the candidate's knowledge of cancer biology and ultimately provide her with the mentoring, skills, and resources needed to achieve her goal to be an independent academic clinical scientist.